content: /**
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
   * compliance with the License. You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License is
   * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
   * the License for the specific language governing permissions and limitations under the License.
   */
  
  package io.reactivex.observable.internal.operators;
  
  import java.util.NoSuchElementException;
  
  import io.reactivex.common.*;
  import io.reactivex.common.internal.disposables.DisposableHelper;
  import io.reactivex.observable.*;
  
  public final class ObservableElementAt<T> extends AbstractObservableWithUpstream<T, T> {
      final long index;
      final T defaultValue;
      final boolean errorOnFewer;
  
      public ObservableElementAt(ObservableSource<T> source, long index, T defaultValue, boolean errorOnFewer) {
          super(source);
          this.index = index;
          this.defaultValue = defaultValue;
          this.errorOnFewer = errorOnFewer;
      }
      @Override
      public void subscribeActual(Observer<? super T> t) {
          source.subscribe(new ElementAtObserver<T>(t, index, defaultValue, errorOnFewer));
      }
  
      static final class ElementAtObserver<T> implements Observer<T>, Disposable {
          final Observer<? super T> actual;
          final long index;
          final T defaultValue;
          final boolean errorOnFewer;
  
          Disposable s;
  
          long count;
  
          boolean done;
  
          ElementAtObserver(Observer<? super T> actual, long index, T defaultValue, boolean errorOnFewer) {
              this.actual = actual;
              this.index = index;
              this.defaultValue = defaultValue;
              this.errorOnFewer = errorOnFewer;
          }
  
          @Override
          public void onSubscribe(Disposable s) {
              if (DisposableHelper.validate(this.s, s)) {
                  this.s = s;
                  actual.onSubscribe(this);
              }
          }
  
  
          @Override
          public void dispose() {
              s.dispose();
          }
  
          @Override
          public boolean isDisposed() {
              return s.isDisposed();
          }
  
  
          @Override
          public void onNext(T t) {
              if (done) {
                  return;
              }
              long c = count;
              if (c == index) {
                  done = true;
                  s.dispose();
                  actual.onNext(t);
                  actual.onComplete();
                  return;
              }
              count = c + 1;
          }
  
          @Override
          public void onError(Throwable t) {
              if (done) {
                  RxJavaCommonPlugins.onError(t);
                  return;
              }
              done = true;
              actual.onError(t);
          }
  
          @Override
          public void onComplete() {
              if (!done) {
                  done = true;
                  T v = defaultValue;
                  if (v == null && errorOnFewer) {
                      actual.onError(new NoSuchElementException());
                  } else {
                      if (v != null) {
                          actual.onNext(v);
                      }
                      actual.onComplete();
                  }
              }
          }
      }
  }
  